Sadly, no connection from Dublin into the 08:00 boat, and no connection to Swansea or beyond (train to Carmarthen only) off the 18:10 bus. Net effect, no connections from Dublin to Swansea / Cardiff (let alone to Bristol or London). All journeys require an overnight at some location. Broken route for tourists.
The 22.14 train from Fishguard Harbour (23.03 on Sundays) runs to
Swansea daily providing a connection out of the 18.10 sailing ex Rosslare (arrives Fishguard Harbour 21.25).
My error? Not sure where I would have got Carmarthen - I tried looking it up for a journey a couple of months back. Perhaps I was unfortunate enough to hit engineering works and rail replacement buses?
I sampled it a few months ago.
Myself and the two other passengers (both off the ferry too; none of us knew each other) were admitted to the waiting room at Swansea (the station shutters are closed for a period in the early hours). The staff encountered were friendly. We were able to board the 03.52 Paddington HST▸ in good time which helped. I alighted at Cardiff - I believe the others were bound for London or beyond. The time actually passed quite quickly. But admittedly it is far from ideal. One wonders would there be merit in the 22.14hrs train (ex FGH) running through to Cardiff particularly at weekends. Of course in an ideal world one could have a slow overnight train the whole way through to Paddington!!! Perhaps not such an outlandish thought
The boat used to run later ... connection off the last train from Dublin, with the 03:52 from Swansea to London starting back at Fishguard Harbour to connect with it. But with only three passengers, some bright spark would turn around and say "no demand", ignoring the current demotivational timing. Alas, the train is no longer the key traffic for that boat, and the boat's timing is to suit the other (road) traffic of cars and lorries.